Geometry is a branch of mathematics that deals with shapes, their sizes, positions, and shape properties. Euclid, a Greek mathematician from 300 BC, is often referred to as the father of geometry due to his influential works. There are two main types of geometry - plane geometry which deals with flat shapes that can be drawn on paper, and solid geometry which involves shapes that have width, depth and height in space, such as cubes and spheres. Plane geometry is used to form solid geometry objects.